A wide variety of downhole well tools may be utilized which are electrically powered. For example, flow control devices, sensors, samplers, packers, instrumentation within well tools, telemetry devices, etc. are available, and others may be developed in the future, which use electricity in performing their respective functions.
In the past, the most common methods of supplying electrical power to well tools were use of batteries and electrical lines extending to a remote location, such as the earth's surface. Unfortunately, some batteries cannot operate for an extended period of time at downhole temperatures, and those that can must still be replaced periodically. Electrical lines extending for long distances can interfere with flow or access if they are positioned within a tubing string, and they can be damaged if they are positioned inside or outside of the tubing string.
Therefore, it may be seen that it would be very beneficial to be able to generate electrical power downhole, e.g., in relatively close proximity to a well tool which consumes the electrical power. This would preferably eliminate the need for batteries, or at least provide a means of charging the batteries downhole, and would preferably eliminate the need for transmitting electrical power over long distances.